The conditions under which two persons will engage in social exchange when individual alternatives to this exchange are concurrently available will be studied in two laboratory experiments using reinforcement principles. Dyads will have the alternatives of obtaining reinforcers by interacting with another person (a social contingency) or by acting independently (an individual contingency). In the first experiment, the establishment of exchange will be studied under six treatment conditions formed by crossing the relationship of the dyad (dependence or interdependence) by the relative reinforcement provided by the social or individual contingencies (social greater for both, individual greater for both, or asymmetrical). In the second experiment, the effects of three variations in reinforcer magnitude on the disruption and re-establishment of social exchange in a dyad in which both persons' social contingencies are stronger will be studied. Ten replications of each condition in each experiment will be conducted under controlled laboratory conditions employing 120 undergraduate subjects in Experiment I and 60 in Experiment II. The experiments will test the validity of the application of operant psychological principles to social exchange under alternative contingencies, and will provide data for comparison with previous applications of operant principles to social exchange under more limited conditions.